We've got a few members on this forum with high mileage reliable 03's. The biggest thing to check for from what I can tell is whether the belt system has been upgraded. Take the seat off and make sure no oil is dripping on the fan, shock or rear cylinder Also the lower fairing wouldn't be able to mount to an aftermarket exhaust without some form of brackets. So as long as he still has the front chin fairing its all good.
if its in good shape I don't see why you wouldn't be able to get the bike for around 2500 or so. Check for the standard leaks and maintenance intervals and if the belt hasn't been upgraded use it as leverage. You may even walk out of there cheaper if you can play it right.